The present invention relates to fuel cell assemblies of the type comprising an assembly of individual cell elements and in particular to the architectures of gaskets between pole plates, and corresponding pole plates.
The cell elements of a fuel cell assembly consist of an assembly of conducting, monopolar or bipolar, plates, sandwiching a membrane structure, and gaskets interposed peripherally between such plates, sealing being achieved when the gaskets between the plates are pressed.
When mounting each cell element, and during subsequent maintenance operations, it is necessary for each cell element to be correctly positioned in the cell pack, preventing any misalignment between cell elements and any pleats or pinching of the interposed gaskets.
One object of the present invention is to propose a gasket/pole-plate architecture that allows easy catching of the gasket on the plates, while ensuring reliable positioning of the gasket.
Another object of the present invention is to propose such a gasket/plate architecture that allows a cell element to be held in place in a closed position before it is fitted into the fuel cell assembly thanks to the shape of the gaskets and plates.
To do this, according to one feature of the invention, a gasket comprises a main part in the form of a polygonal, typically rectangular, frame and, in at least two diagonally opposed corners of the frame, a projecting part forming at least a first loop for catching on the edge of a plate.
According to another feature of the invention, the projecting part of the gasket includes a second loop for catching on the edge of the other plate of the pair of plates constituting a cell element.
According to one aspect of the invention, a pole plate of a cell element comprises, on at least one face, an array of fluid circulation channels and, on their periphery, a slot of rectangular general configuration, intended to house a gasket, and, in at least two diagonally opposed corners, at least one lug for catching a loop of the gasket.
According to particular features of the invention:                the slot has a trapezoidal cross section; and        the gasket has, on one of its main faces, a longitudinal slot.        
Another subject of the present invention is a cell element of a fuel cell assembly, consisting of a pair of adjoined plates, each provided with a gasket, such as the plates and gaskets defined above.
Another subject of the invention is such a cell element assembled by catching the gasket onto the plates.
A final subject of the invention is a fuel cell assembly comprising a stack of such cell elements.
In the embodiment shown in FIG. 1, there is a pole plate 1, of flat rectangular general configuration, comprising, on one face, an array of fluid distribution channels 2, a peripheral slot for housing a resilient gasket 3, as will be seen later, and, on its other face, parallel fluid circulation channels 4 (cf. FIG. 3).
As may be seen in FIG. 2, the gasket 3 has a general configuration in the form of a rectangular frame, of rectangular cross section, intended to be housed in a corresponding rectangular slot 5 in the plate (cf. FIG. 6) with, in at least two diagonally opposed corners, advantageously in the four corners, a projecting part forming a loop 6 that catches resiliently, in the assembly configuration, on a corresponding internally projecting lug 7 of the plate 1. The gasket 3 may thus be correctly placed, under slight tension, in the slot 5 of the plate 1.
According to one aspect of the invention, the gasket 3 includes, in at least one of its corners, another loop 8 that extends cantileveredly outwards from the adjacent first loop 6. As may be better seen in FIGS. 4 and 5, this external loop 8 of the gasket of a pole plate is intended to be bent over and resiliently caught around at least one other projecting part 9 of the other plate, this resilient catching thus making it possible for the two plates applied against each other to be held in place in a unitary subassembly as shown in FIG. 3.
According to other aspects of the invention, each gasket 3 includes, on one of the short sides of the rectangle, at least one tab 10 resiliently housed, by gently force-fitting it, in a corresponding recess provided on the periphery of the plate 1, and also at least one tongue 11 projecting externally and associated with a corresponding protuberance 12 on the pole plate 1 in order to form, in the assembled configuration, jaws for clamping a conductor or a terminal of an electronic component 13 associated with the cell element for measuring the voltage of the latter.
As may be seen in FIG. 3, each pole plate 1 has, on one of its short sides, outwardly opening beveled channels 14 for mounting structures for connecting the fluid channels 2 to external fluid circuits, as described in patent application FR 04/51375 of Jun. 30, 2004, in the name of the Applicant.
According to one aspect of the invention, the sectional view on a larger scale in FIG. 6 shows the proton exchange membrane 15 clamped with its gas diffusion layer 16 between the pole plates 1, the slot 5 for housing the gasket 3, made of a low-creep resilient material, said slot having a trapezoidal shape, and the gasket 3 having a rectangular cross section, making it possible to achieve a seal with lower compressive forces, while still fitting the gasket into the correct position in the slot. To make it even easier to position the gasket in the slot, the gasket 3 may have, on its lateral faces, parallel vertical ribs or beads 17. In addition, to guarantee correct elastic deformation of the gasket 3 in the slot 5, said gasket includes, on one of its main faces, a longitudinal slot 18. Advantageously, in the assembled configuration, as shown in FIG. 6, the groove 18 of one of the gaskets 3 is positioned against the bottom of the corresponding slot 5, the groove in the other gasket being positioned against the membrane 15.
Advantageously, the pole plates 1 are conventionally produced, these being based on carbon, typically by molding a graphite-based powder. The gaskets 3 are made of elastomers, for example Viton, butyl, EPDM, Hytrel, silicone, etc.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.